Pre-programmable optical filtering / amplifying method and apparatus

Abstract

An optical amplification method which includes a spectral filtering method for selecting one of several pre-recorded spectral filter patterns and applies this filter to the spectral distribution of a multi-wavelength optical signal transmitted from an input to an output fiber. Optical filtering may be accomplished using free-space bulk optical diffractive wavelength demultiplexing, combined with a fixed (permanent) spatial pattern located in the spectrally dispersed image plane, to transfer to the optical output fiber the input signal with its spectrum selectively attenuated.

1 . A optical amplification method comprising the steps of: 
 receiving an optical signal for amplification;    selecting, a pre-programmed filter from a plurality of such filters;    applying, the selected filter to the received signal; and    amplifying the filtered signal.    
   
   
       2 . The amplification method according to  claim 1  further comprising the step of: 
 collecting control system input sufficient to select filtering characteristics.    
   
   
       3 . The amplification method according to  claim 1  wherein the pre-programmed filter is one of a set of predetermined filter profiles wherein each one of the set has an arbitrary shape.  
   
   
       4 . A optical amplification method comprising the steps of: 
 receiving an optical signal for amplification;    amplifying the received signal;    selecting, a pre-programmed filter from a plurality of such filters; and    applying the amplified signal to the selected filter.    
   
   
       5 . The amplification method according to  claim 5  further comprising the step of: 
 amplifying the filtered signal.    
   
   
       6 . The amplification method according to  claim 5  further comprising the step of: 
 collecting control system input sufficient to select filtering characteristics.    
   
   
       7 . The amplification method according to  claim 5  wherein the pre-programmed filter is one of a set of predetermined filter profiles wherein each one of the set is an arbitrary shape.  
   
   
       8 . A method of controlling/maintaining gain in an optical amplifier comprising the steps of: 
 collecting, control system input pertaining to a received optical signal, sufficient to select a pre-programmed filter from a plurality of such filters;    selecting, the pre-programmed filter; and    applying the signal to the filter;    such that the gain of the optical amplifier substantially achieves a desired profile as a function of optical signal wavelength.    
   
   
       9 . The method according to  claim 8  wherein the selected filter is an arbitrary, pre-determined one wherein the pre-programmed filter is one of a set of predetermined filter profiles wherein each one of the set has an arbitrary shape.  
   
   
       10 . The method according to  claim 9  further comprising the step of: 
 adjusting dynamically the spectral tilt of the gain profile of optical amplifier.    
   
   
       11 . The method according to  claim 10  wherein the dynamic adjusting is performed as a function of channel loading.  
   
   
       12 . The method according to  claim 11  wherein the dynamic adjusting is performed as function of input power to the amplifier.  
   
   
       13 . The method according to  claim 8  in which the control system information pertaining to the optical signal includes a measure of the gain at one or more erbium stages of the amplifier.  
   
   
       14 . The method according to  claim 8  further comprising the step of: 
 blocking of one or more wavelengths by the optical amplifier as a function of the input to the control system.    
   
   
       15 . An optical filter comprising: 
 a pre-programmed fixed optical spatial filter;    an optical system for dispersing an input spectrum on to said filter wherein said optical system includes:    a lateral position control system for controlling the lateral position of the dispersed spectrum on the pre-programmed fixed optical spatial filter positioned at the demultiplexed spectral plane; and    an optical system for collecting the dispersed, filtered spectrum and directing it as an output spectrum.    
   
   
       16 . The optical filter according to  claim 15  wherein said pre-programmed fixed optical spatial filter is a 2-D optical phase filter.  
   
   
       17 . The optical filter according to  claim 15  wherein said pre-programmed fixed optical spatial filter is an amplitude filter.  
   
   
       18 . The optical filter according to  claim 15  wherein said pre-programmed fixed optical spatial filter is a reflection filter.  
   
   
       19 . The optical filter according to  claim 15  wherein said lateral position control system includes a tilting reflective surface to control the lateral position of the dispersed spectrum.  
   
   
       20 . The optical filter according to  claim 15  wherein said lateral position control system includes a transmissive linear phase controller to control the lateral position of the dispersed spectrum.  
   
   
       21 . The optical filter according to  claim 15  including an input fiber lateral shifter for controlling the position of the dispersed spectrum.  
   
   
       22 . The optical filter according to  claim 15  including a filter shifter for controlling the position of the dispersed spectrum.  
   
   
       23 . The optical filter according to  claim 15  further comprising a detector for detecting the position of the dispersed spectrum on the optical filter.  
   
   
       24 . An optical amplifier comprising: 
 means for receiving an optical signal;    means for selecting a pre-programmed filter from a plurality of such filters;    means for applying the selected filter to the optical signal; and    means for amplifying the optical signal.    
   
   
       25 . The optical amplifier according to  claim 24  further comprising: 
 means for collecting control system information sufficient to select the pre-programmed filter.    
   
   
       26 . The optical filter according to  claim 25  wherein the pre-programmed filter is one of a set of predetermined filter profiles wherein each one of the set has an arbitrary shape.